Process of remelting iron in cupola-furnaces



(No Model.)

Patented Sept. 28, 1890.

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UNITED STATES PATENT OFFICE.

HENRY J. GRAF, OF ST. LOUIS, MISSOURI.

PROCESS OF REMELTING IRQN IN CUPOLA-FURNACES.

SPECIFICATION forming part of Letters Patent No. 437,109, datedSeptember 23, 1890.

Application filed February 25, 1890. Serial No. S LL'YOB. (Nospecimens.)

To all whom it may concern.-

Be it known that I, HENRY J. GRAF, of St. Louis, in the State ofMissouri, have invented certain new and useful Improvements in theProcess of Remelting Iron in Cupola-Furnaces, of which the following isa full, clear, and exact description, reference being bad to theaccompanying drawings, forming a part hereof.

Heretofore in remelting iron in a cupolafurnace for the production ofcastings the air that is blown in has come in contact with the liquidmetal and the carbon-thereof, and the metal is decarbonized to aconsiderable extent, and the oxide is correspondingly increased inquantity. The iron having been left too long in such semi-fluidcondition subject to the action of the blast, the oxygen has united withthe carbon of the iron and converted a considerable portion of it intosteel. The iron has therefore lost a corresponding percentage ofgraphitic carbon, retaining only combined carbon. Iron melted under suchconditions does so very slowly, and drops down into the semi-fluid massat the bottom of the cupola and deteriorates the quality of same,causing hard spots in the castings. Furthermore, such iron having lostuncom bined carbon will be less fluid, and the result will be imperfectcastings.

The objects of my invention may be briefly stated as follows: Toincrease the outflow of carbonic acid; to increase the temperature ofthe furnace, using less fuel and blastpressure than are at presentnecessary; to retain great heat at the bed and permit but little toescape at top of furnace or charging door; to decrease the quantity ofcoke now used in the bed and between charges 5 to provide a materialwhich shall act as a flux; to prevent decarbonization during the meltingprocess, and to improve the quality of lowgrade iron, such as scrap, &c.

To these ends my invention consists in charging the furnace with scrapor pig iron, ignited coke, and gas-carbon in alternate layers, wherebythe iron is segregated from the direct action of the mass of the blastand caused to receive a diffused blast, and whereby the iron is keptfrom a long continuation of that blast, thus preventing a great loss ofcarbon, and placing the iron in such a position that when melted it willreach and take up a larger proportion of graphitic carbon. Thissegregation and location of the iron is effected by the interposition ofthe gas-carbon beneath the iron and between it and the fuel, as will behereinafter more fully described and claimed.

1 will now proceed to describe more specifically the manner of carryingout my invention, and for facility in doing the same I have illustratedapparatus suitable therefor.

Inthe drawings, Figure 1 is a vertical sec tion of an ordinarycupola-furnace, and Fig. 2 is a perspective view of a detached andenlarged particle of gas-retort carbon made use of in carrying out theinvention.

Like letters refer to like parts in .the two figures.

A indicates the outer shell of an ordinary cupola, the same beingprovided with a suitable lining upon its interior, and being mountedupon suitable iron columns, (or a base of masonry,) such as B. Thisshell is provided with a drop-bottom O, and in use should also have asand-bed D. Tuyeres E, slag-hole F, and tap-hole H are also provided inthe usual 7 manner, as is also a straight open-topped stack and acharging-opening I.

The direct or natural draft is used in starting the fire, as is usual inthese cases.

My improved method of charging the furnace and the material employedtherein is as follows: I first place a charge of ordinary coke J on thebottom of the furnace, which forms a base or stratum upon which the nextadjacent stratum is adapted to rest. This bed-stratum is then ignitedand the blast is turned on. Then a thinner stratum of gas-1e tort carbon(commonlyknown as suchin other usages) K is placed upon the coke-stratumJ, said gas-retort carbon having previouslybeen broken up to about whatis known in the coal trade as egg size. After the charge of gasretortcarbon has been thrown into the furnace it is evenly distributed overthe cokestratum, or it may be distributed properly during the process ofthrowing it in, thus giving it the best opportunity to ignite.

L is a charge of iron, in the form of pig, scrap, or otherwise, scrapbeing preferred, as

its cost is low and its quality will beimproved suflicient for use inhigh-grade castings.

M is a small charge of coke.

N is another stratum of gas-retort carbon, and O is another charge ofiron, and so on until the required amount of iron is melted.

In carrying out the usual process of treating iron in cupola'furnacesthe air that is blown into the furnace contains aqueous Vapors, and bytheir action upon the liquid metal and carbon the former becomesdeearbonized and liberates the latter in the form of a gas, while if thesemi-fluid iron is subjected to the blast and cold air for too great alength of time it falls down into the molten metal and the latterdeteriorates. These troubles I overcome by using the aforesaid carbonand by using the same amount of blast that is commonly used until thecarbon is ignited, when I decrease the blast about fifty per cent. Bythese means carbonic-acid gas is not driven out of the stack of thefurnace in such great quantities has been previously the ease, and theamount of aqueous Vapors passing through the cupola is decreased. As thetemperature is thus increased the iron is rapidly fused, it being leftfor a short time only subjected to the cold air, and as the carbon ismelted it is precipitated into the iron, thus leaving it whollyuncombined and in a graphitic state.

By my process above described fifty per cent. less fuel (coke) isrequired between charges of iron during the melting operation, and Ihave found that fifty per cent. less blast is required to accomplish theresults aforesaid, and therefore heat will not be thrown out of thecharging-opening and top of furnace, asheretofore. About two percent. ofgas-retort carbon to one hundred per cent. of good scrap or pig isrequired.

I am aware that previous to my invention carbon has been blown throughmolten iron, (the carbon being in the form of a powder and beingintroduced within the cupola through the tuyeres,) and that iron hasbeen melted by the use of carbon alone, and I do not therefore desire toclaim such a process; but

'What I do claim, and desire to secure by Letters Patent, is-

1. The herein-described process for remelting and refining iron incupola-furnaces, which consists in subjecting alternate layers of scrapor pig iron, ignited coke, and gas carbon to a blast, as and for thepurpose described.

2. The hereinbefore-described process of treating iron incupola-furnaces, which consists, first, in charging the said iron inlayers and alternately with a layer of gas-carbon and a layerof coke;second, blowing air therethrough until the carbon is ignited, and,third, reducing the amount of the said air-blast, as described.

In testimony whereof Iaflix mysignature in presence of two witnesses.

HENRY J. GRAF.

\Vitnesses:

JNo. (l. IIIonoN, U. K. JONES.

